Work will be concentrated in the following areas: Pathogenesis of immune throbocytopenias; characterization of platelet auto- and iso-antigens; immunologic aspects of platelet transfusion therapy - Methods of detecting iso-, auto and drug-dependent antibodies reactive with human platelets will be further refined with particular attention to techniques involving immunofluorescence. Expression of HLA antigens on platelets and its genetic control will be investigated. Platelet membrane receptors reactive with anti-P1A1 alloantibodies and drug-dependent, platelet-specific antibodies and their relationship to platelet function will be further characterized. Guidelines for "matching" of platelets for transfusion to alloimmunized recipients will be further defined. Molecular basis of the platelet "storage lesion" - Biochemical and structural changes occurring in platelets during isolation and short-term storage will be further characterized. Findings will be applied to the development of improve methods of short-term platelet preservation.